The invention relates to a condenser system for a phase-contrast illumination system for microscopes and to a condenser system for a fringe-contrast illumination system for microscopes.
In condenser systems for a phase-contrast illumination system in microscopes, it is known to use different condensers with a set of light rings specially adapted to each individual condenser. A set of light rings contains individual light rings having different light ring diameters. In microscopes having various objectives of differing magnifying power, it is usually necessary to make available a plurality of different light rings having different diameters per condenser. It has previously been necessary for this combination of condenser and set of light rings to be arranged in a mechanically expensive way in the illuminating beam path. The arrangement of the set of light rings with the associated condenser optical system in the illuminating beam path was made in a known embodiment such that the set of light rings was arranged together with the condenser optical system in a separate nosepiece. The entire nosepiecc was exchanged when changing the condenser optical system. However, this required the exchanging guides of the nosepiece and the guides on the microscope to be precisely manufactured, and in addition required adjusting elements for centering the condenser to be made available. In addition to the substantial manufacturing outlay for such exchangeable nosepieces, it is also disadvantageous in this known solution that a special set of light rings in a special nosepiece must be made available for each condenser optical system.
DE 23 37 653, which corresponds to U.S. Pat. No. 3,790,254, discloses a condenser system for phase-contrast illumination system in microscopes, in which a plurality of condensers having the same focal length and different free working distances are represented and described. Owing to this special row of condensers, a single set of light rings can be used for different condensers.
However, in practice the row of condensers described can be used only to a limited extent, since it is possible to realize optically only a free working distance amounting to a maximum of 5.5 mm. At larger distances, up to 70 mm, such as are urgently required in inverted microscopes for viewing objects in petri dishes, microtitration plates, culture flasks and the like, optical reasons preclude the realization of a constant focal length of the different condenser optical systems.
In known condenser systems for a fringe-contrast illumination system with microscopes, there is likewise the problem that the very expensive Wollaston prisms have to be adapted to the objectives employed, which have different magnifying powers, and to condenser optical systems. There is a need here, as well, for a plurality of specially built prisms for each condenser optical system which are likewise arranged in a nosepiece plate upstream of the condenser. The use of the prisms depends in this case on the respective magnifying powers and focal lengths of the objectives and condenser optical systems.